gen.freq.curves {lmomco} | R Documentation

## Plot Randomly Generated Frequency Curves from a Parent Distribution

### Description

This function generates random samples of specified size from a specified parent distribution. Subsequently, the type of parent distribution is fit to the L-moments of the generated sample. The fitted distribution is then plotted with the built-in function `lines`. It is the user's responsibility to have an active `plot` already drawn; unless the `callplot` option is `TRUE`. This function is useful to demonstration of sample size on the uncertainty of a fitted distribution—a motivation for this function is for class room exercise.

### Usage

    gen.freq.curves(n, para, F=NULL, nsim=10, callplot=TRUE,
    aslog=FALSE, asprob=FALSE, showsample=FALSE, showparent=FALSE, ...)

### Arguments

`n` | Sample size to draw from parent as specified by `para`.
`para` | The parameters from `lmom2par` or similar.
`F` | The nonexceedance probabilities for horizontal axis—defaults to `nonexceeds` when the argument is `NULL`.
`nsim` | The number of simulations to perform (frequency curves to draw)—the default is 10.
`callplot` | Calls `plot` to acquire a graphics device—default is `TRUE`, but the called `plot` is left empty.
`aslog` | Compute `log10` of quantiles—note that
    NaNs produced in: log(x, base)
will be produced for less than zero values. Otherwise this is a harmless message.
`asprob` | The `qnorm` function is used to convert nonexceedance probabilities, which are produced by `nonexceeds`, to standard normal deviates. The normal distribution will plot as straight line when this argument is `TRUE` and `aslog=FALSE`.
`showsample` | Each simulated sample is drawn through plotting positions (`pp`).
`showparent` | The curve for the parent distribution is plotted on exit from the function if `TRUE`. Further plotting options can not be controlled—unlike the situation with the drawing of the simulated frequency curves.
`...` | Additional parameters are passed to the `lines` call within the function—except for the drawing of the parent distribution (see argument `showparent`.

### Value

No value is returned. This function is used for its graphical side effects.

### Author(s)

W.H. Asquith

### See Also

`lmom2par`, `nonexceeds`, `rlmomco`, `lmoms`

### Examples

    para <- vec2par(c(140,4),type='gam') # build a gamma parent
    F    <- nonexceeds() # vector of nonexceedance probabilities
    Q    <- quagam(F,para) # the quantiles of parent distribution
    # simulated are grey, parent is black
    gen.freq.curves(10,para,nsim=15,asprob=TRUE,showparent=TRUE,col=8)

[Package lmomco version 0.92 Index]